1. Related Application
This application is a continuation-in-part application of my copending application Ser. No. 598,772, filed July 24, 1975, entitled "HIGH SPEED ROTARY BRANDING PROCESS HAVING INCREASED DIE LIFE," issued on Feb. 15, 1977 as U.S. Pat. No. 4,007,767. My copending application Ser. No. 598,772 is a continuation-in-part application based upon application Ser. No. 440,481, filed on Feb. 7, 1974 and entitled HIGH TEMPERATURE, LOW PRESSURE AND HIGH SPEED WOOD GRAIN EMBOSSING PROCESS, which application is now abandoned, but which application was in turn a divisional application of application Ser. No. 216,061, filed Jan. 7, 1972 and entitled HIGH SPEED, HIGH TEMPERATURE EMBOSSING MACHINE AND WHEEL THEREFOR, issued as U.S. Pat. No. 3,730,081 on May 1, 1973 with the title ROTARY HOT DIE EMBOSSER WITH TAPERED SHAFT AND INSULATED EMBOSSING WHEEL.
2. Prior Art
Highspeed rotary embossing apparatus have previously been devised which are particularly well suited for use in the embossing of relatively soft wooden molding for furniture, picture frames and the like. U.S. Pat. Nos. 3,730,081 and 3,764,767 typify such prior art apparatus, and the product produced therefrom is soft lumber with a deep coarse pattern branded therein.
In addition to embossing wood molding, it has long been desirable to be able to emboss a wood grain pattern on sheets or panels of wooden materials having poor grain characteristics. Such embossing of wooden panels has been accomplished to a limited degree by the apparatus of U.S. Pat. Nos. 2,703,463 and 2,695,857 which employ low temperature, low speed, high pressure processes. The resultant product is a relatively soft wooden panel, such as a plywood or the like.
The apparatus of U.S. Pat. Nos. 3,294,041 and 3,393,294 produce wood products having simulated wormholes therein. U.S. Pat. No. 2,202,110 teaches the use of hot blades to incise or cut soft woods such as Douglas fir.
In addition, cold dies have been employed with very substantial pressures to attempt to crush or impress a wood grain pattern into a wooden article. Even when relatively soft wood is employed, this approach results in chipping and fracturing of the wood fiber, poor grain definition, slow speed and inability of the impressed grain to visually stand out from the remainder of the wood with a corresponding need to use inks or color fillers to bring out the grain.
In addition to branding or embossing a pattern onto panels and molding, printing processes have been employed in which ink in imprinted onto the article in a wood grain pattern. In this process, the finish of the panel is controlled by the grain printer, and the manufacturer of the article must attempt to match other wood to the finish of the printed wood. Sanding or other refinishing of wood grain printed products is impossible.
Although there has been considerable effort in connection with attempts to upgrade wooden products having poor grain quality to products which have a desirable wood grain appearance, little or nothing has been done in connection with another common building material, namely, plasterboard. Plasterboard, sometimes called sheetrock and drywall, is formed as a sandwich of two paper or felt sheets which are bonded to a central hardened gypsum core. Plasterboard generally comes in relatively large sheets, for example, 1.2 .times. 2.4 meters and in thicknesses ranging from about 6 to 25 millimeters. Such plasterboard has been widely used for many years as a backing or substitute for plaster in the construction of residences, offices and numerous other buildings. While plasterboard does afford many advantages in building construction, one of its disadvantages is that it must always be covered by another material, such as paneling, paint, plaster, etc. The outside surfaces of the plasterboard are usually unacceptable as a final structural surface.
Essentially, therefore, the building industry has simply used plasterboard as a structural, and not a decorative, product. Thus, plasterboard is supplied to builders and the like with a plain, often gray, outer surface which is totally devoid of surface ornamentation, other than the manufacturer's trademark.